A double-hung window assembly typically includes a window frame and a pair of window sashes mounted for vertical reciprocal sliding movement, one relative to the other, in guide rails of the master frame jamb of the window assembly. Although window sashes traditionally have been made exclusively of wood, such window sashes now can be formed of extruded plastic frame members or metal frame members which are joined at mitered corners, for instance, to form a generally rectangular frame in which the glazing is mounted. One type of such a window sash is described, for example, in U.S. Pat. No. 4,578,903 having the same inventor and assignee of the present invention.
Window sashes also are known which include a sash lock or fastener which, when the sash is closed, automatically locks and holds the sash in the closed position. The fastener includes a rectangular casing having an opening at its front end or faceplate in which opening a tumbler or dog is mounted, the casing being mortised into the upper sash and secured therein by screws. The tumbler is mounted within the casing by a guiding device so that the tumbler may be pivotally projected forward or longitudinally to overlie the lower sash and also to be moved laterally when projected forward to engage the casing and lock itself in position. The tumbler is biased in the projected position by a coiled, safety pin type spring mounted within the casing. One type of such a window sash is disclosed, for example, in U.S. Pat. No. 534,185.
Sash security looks or fasteners similar to that disclosed in U.S. Pat. No. 534,185 currently are produced and still employ the safety pin type coil spring described hereinabove. It has been found that in the assembly of such sash locks, the coiled spring is unwieldy and difficult to properly position within the casing thereby contributing to an increase in the labor expenses necessary for their installation.
U.S. Pat. No. 4,824,154, having the same inventor and assignee as the present invention, overcame the disadvantages of the above prior art by providing a security lock for a double-hung sash window assembly which is to be mounted on a stile of a first sash frame to limit movement of the second sash frame relative to the first sash frame. The security lock includes a casing adapted to be mounted within a recess in one of the sash frames, a faceplate of the casing having an opening therein communicating with and overlaying an interior casing cavity. A tumbler is pivotally mounted in the cavity and is spring biased to project through the opening to engage and lock the second sash. A leaf spring is mounted within the casing cavity so that one end of the leaf spring can bias the tumbler into its locking position, while permitting the tumbler to be retracted into the casing. The opposite end of the leaf spring protrudes from the casing into engagement with a side of the stile for retaining the security lock installed in the stile recess. This type of security lock is not desirable in some applications due to the protruding end of the leaf spring, provides no indication to a user that the tumbler is in its locked position, and provides no positive containment of the tumbler in the locked position.
The security lock embodying the invention utilizes a leaf spring which is completely contained within the lock casing and which provides a positive indication and a releasable securement of the tumbler in the locked position. The security lock is designed to enable the lock to be assembled easily and rapidly at reduced labor costs for supply to the window manufacturer for direct installation into the window sash.